Semiconductor structure and fabrication method thereof

Abstract

A fabrication method for a semiconductor structure at least includes the following steps. First, a pattern mask with a predetermined layout pattern is formed on a substrate. The layout pattern is then transferred to the underneath substrate so as to form at least a fin-shaped structure in the substrate. Subsequently, a shallow trench isolation structure is formed around the fin-shaped structure. Afterwards, a steam oxidation process is carried out to oxidize the fin-shaped structure protruding from the shallow trench isolation and to form an oxide layer on its surface. Finally, the oxide layer is removed completely.

1 . A method for fabricating a semiconductor structure, comprising:
 forming at least a patterned mask on a substrate, wherein the patterned mask has a layout pattern;   transferring the layout pattern into the substrate so as to form at least a fin structures in the substrate;   forming a shallow trench isolation structure around the fin structures;   performing a steam oxidation process so as to oxidize the fin structure protruding from the shallow trench isolation structure and form an oxide layer; and   completely removing the oxide layer.   
     
     
         2 . The method according to  claim 1 , further comprising a pad layer disposed between the patterned mask and the substrate. 
     
     
         3 . The method according to  claim 2 , further comprising transferring the layout pattern into the pad layer so as to form a patterned pad layer. 
     
     
         4 . The method according to  claim 3 , further comprising removing the patterned pad layer before performing the steam oxidation process. 
     
     
         5 . The method according to  claim 1 , further comprising performing another steam oxidation process before forming the shallow trench isolation structure. 
     
     
         6 . The method according to  claim 1 , wherein a step for forming the shallow trench isolation structure comprises:
 blank depositing an insulating layer, conformally covering the patterned mask and the fin structure;   polishing the insulating layer until the patterned mask is exposed; and   performing an etching process until a top portion of the fin structure protrudes from the insulating layer.   
     
     
         7 . The method according to  claim 1 , wherein a top portion of the fin structure protrudes from the shallow trench isolation structure before performing the steam oxidation process, wherein the top portion comprises a top surface and a bottom surface, and a ratio of a width of the top surface to a width of the bottom surface ranges from ⅓ to ½. 
     
     
         8 . The method according to  claim 7 , wherein the bottom surface of the top portion is leveled with a top surface of the shallow trench isolation structure. 
     
     
         9 . The method according to  claim 7 , wherein a ratio of the width of the top surface to the width of the bottom surface ranges from ¼ to ⅓ after completely removing the oxide layer. 
     
     
         10 . The method according to  claim 1 , wherein a recipe of the steam oxidation process comprises water and oxygen. 
     
     
         11 . The method according to  claim 1 , wherein a temperature of the steam oxidation process ranges from 750° C. to 1000° C. 
     
     
         12 . The method according to  claim 1 , further comprising performing at least an ion implantation process before completely removing the oxide layer. 
     
     
         13 . The method according to  claim 1 , wherein a thickness of the oxide layer gradually increase from bottom to top. 
     
     
         14 . The method according to  claim 1 , wherein a top portion of the fin structure protrudes from the shallow trench isolation structure after completely removing the oxide layer, wherein the top portion comprises a top surface and a bottom surface, a ratio of a width of the top surface to a width of the bottom surface ranging from ¼ to ⅓. 
     
     
         15 . The method according to  claim 1 , further comprising performing a thermal treatment after completely removing the oxide layer. 
     
     
         16 . The method according to  claim 15 , wherein a temperature of the thermal treatment ranges from 900° C. to 1200° C. 
     
     
         17 . The method according to  claim 1 , further comprising performing a surface treatment after completely removing the oxide layer, wherein a recipe of the surface treatment comprises hydrogen and nitrogen. 
     
     
         18 . A semiconductor structure, comprising:
 a fin structure, disposed on a substrate, wherein at least one of sidewalls of the fin structure comprises at least two slanted surfaces, and an interface is formed between the slanted surfaces; and   a shallow trench isolation structure, disposed on the substrate and around the fin structure, wherein a top surface of the shallow trench isolation structure is substantially leveled with the interface.   
     
     
         19 . The structure according to  claim 18 , wherein the slanted surfaces at least comprise a first slanted surface and a second slanted surface, a first angle is defined between the first slanted surface and the top surface of the substrate, a second angle is defined between the second slanted surface and the top surface of the shallow trench isolation structure, wherein the first angle is greater than the second angle, and both the first angle and the second angle are in the fin structures. 
     
     
         20 . The structure according to  claim 18 , wherein the fin structure has a profile shrinking from bottom to top.